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Thread: Spark Plugs

  1. #1

    Question Spark Plugs

    For 4 stroke outboards, what's your opinion on plug changes? Personally, I pull them, check for corrosion and pitting, if they look good I put them back in. Am I being naive, or is there more than this to be concerned with? I've never been the one to do something "because you never know" or "it can't hurt" tells me to.
    We never really grow up, we only learn
    how to act in public

  2. #2
    Member breausaw's Avatar
    Join Date
    Oct 2006


    The Way I see it plugs are inexpensive; if you bother to pull them out why not put in fresh platinumís. The service manual for my Honda says replace each year or 200 hours, who am I to argue. Carry a complete replacement set on the boat also.
    07 C-Dory 25 Cruiser

  3. #3
    Member ACBMAN's Avatar
    Join Date
    May 2006
    Anchorage only because that's where the work is


    Changed mine at 400 hours on twin 225 Yamaha 4 strokes just because,6 dollars each x12 and it runs they run the same as before which is great.

  4. #4

    Default Good Point

    Not that cost is a factor on a boat anyway, I was just curious about the physical science side of it. Is there anything else that breaks down on spark plugs besides the electrodes that would inspire replacement?
    We never really grow up, we only learn
    how to act in public

  5. #5


    My experience from racing bikes and sleds (snow machines) is that they can look fine and the electrode can still break off. Granted these were race machines and we were messing with the timing to gain performance. If that tiny piece of metal doesn't get spit out the exhaust quickly it can do some expensive damage. Cost of a new plug is cheap in comparison. I replaced often when I was racing and could tell difference but the difference would be impossible to feel in a large boat but I still replace them according to the manual. Cheap insurance.


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